1. Field of the Invention
The present invention relates to a process and an apparatus for measuring rheological properties of semi-solid bodies by harmonic shear in rotation. The said apparatus can be called a viscoelastometer.
The invention makes it possible to study both simple rheological properties (viscosity, elasticity) and complex rheological properties (viscoelasticity, plasticity, viscoplasticity, etc.) of numerous semi-solid bodies or substances.
The applications of the present invention are very numerous.
Examples of semi-solid products are represented by products in the form of gels and creams. There may be mentioned in particular the gels of gelatine, starch, milk, ice creams, marshmallow, jam, chocolate creams, honey, dairy cream and other food products, as well as coagulated blood and similar semi-solid substances.
The present invention also has an application in the plastics industry, rubber industry, wax industry and petroleum products industry.
The invention applies generally to all the semi-solid bodies. Nevertheless, it has a particular application in the cheese industry for choosing the time for cutting the coagulum or curd in cheese making.
The invention employs a harmonic rotational shear and makes it possible to measure the required physical quantities accurately in international system units.
Because of the low shear produced in the product, the structure of the product is not destroyed and it is possible to follow the change in its rheological properties with time.
The apparatus is completely automatic and can be employed in the laboratory as well as in control systems and in industrial manufacturing systems.
It is known that rheology is a field of technology concerned with the study of relationships between stresses and strains.
The subject of the present invention is a process for measurement and a measuring apparatus of a design which is, at the same time, simple, efficient and reliable and permits a deformation to be produced in a semi-solid product through the intermediacy of a measuring head oscillating around its vertical axis and driven with a sinusoidal of pseudo-sinusoidal rotational movement with controllable frequency and amplitude, the measurement of the torque produced in the product around the head being carried out by a torque sensor mounted on the axle or shaft.
So far as it is known, there is at the present time no known apparatus for measuring rheological properties of semi-solid bodies in which the axle carrying the measuring head is driven in a perfectly sinusoidal rotational movement.
2. Description of the Prior Art
In the prior art use is made of a special apparatus for milk, known under the name of Torsiometer, marketed by the Company Plint and Partners in which the amplitude and the frequency of oscillation of the cylinder are fixed. This apparatus is manual and its torque measuring system cannot provide international system units.
Such an apparatus can only work with a wide gap (the gap being the distance between the measuring head and the wall of the vessel) and its motion is not constant in the course of the gelling of the milk.